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dfs.hh
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00001 /* -*- mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- */
00002 /*
00003  *  Main authors:
00004  *     Christian Schulte <schulte@gecode.org>
00005  *
00006  *  Copyright:
00007  *     Christian Schulte, 2009
00008  *
00009  *  Last modified:
00010  *     $Date: 2009-08-26 21:10:00 +0200 (Wed, 26 Aug 2009) $ by $Author: schulte $
00011  *     $Revision: 9632 $
00012  *
00013  *  This file is part of Gecode, the generic constraint
00014  *  development environment:
00015  *     http://www.gecode.org
00016  *
00017  *  Permission is hereby granted, free of charge, to any person obtaining
00018  *  a copy of this software and associated documentation files (the
00019  *  "Software"), to deal in the Software without restriction, including
00020  *  without limitation the rights to use, copy, modify, merge, publish,
00021  *  distribute, sublicense, and/or sell copies of the Software, and to
00022  *  permit persons to whom the Software is furnished to do so, subject to
00023  *  the following conditions:
00024  *
00025  *  The above copyright notice and this permission notice shall be
00026  *  included in all copies or substantial portions of the Software.
00027  *
00028  *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
00029  *  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
00030  *  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
00031  *  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
00032  *  LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
00033  *  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
00034  *  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
00035  *
00036  */
00037 
00038 #ifndef __GECODE_SEARCH_SEQUENTIAL_DFS_HH__
00039 #define __GECODE_SEARCH_SEQUENTIAL_DFS_HH__
00040 
00041 #include <gecode/search.hh>
00042 #include <gecode/search/support.hh>
00043 #include <gecode/search/worker.hh>
00044 #include <gecode/search/sequential/path.hh>
00045 
00046 namespace Gecode { namespace Search { namespace Sequential {
00047 
00049   class DFS : public Worker {
00050   private:
00052     Options opt;
00054     Path path;
00056     Space* cur;
00058     unsigned int d;
00059   protected:
00061     Space* reset(Space* s);
00062   public:
00064     DFS(Space* s, size_t sz, const Options& o);
00066     Space* next(void);
00068     Statistics statistics(void) const;
00070     ~DFS(void);
00071   };
00072 
00073   forceinline 
00074   DFS::DFS(Space* s, size_t sz, const Options& o)
00075     : Worker(sz), opt(o), d(0) {
00076     cur = (s->status(*this) == SS_FAILED) ? NULL : snapshot(s,opt);
00077     current(s);
00078     current(NULL);
00079     current(cur);
00080     if (cur == NULL)
00081       fail++;
00082   }
00083 
00084   forceinline Space*
00085   DFS::reset(Space* s) {
00086     delete cur;
00087     path.reset();
00088     d = 0;
00089     if (s->status(*this) == SS_FAILED) {
00090       cur = NULL;
00091       Worker::reset();
00092       return NULL;
00093     } else {
00094       cur = s;
00095       Worker::reset(cur);
00096       return cur->clone();
00097     }
00098   }
00099 
00100   forceinline Space*
00101   DFS::next(void) {
00102     start();
00103     while (true) {
00104       while (cur) {
00105         if (stop(opt,path.size()))
00106           return NULL;
00107         node++;
00108         switch (cur->status(*this)) {
00109         case SS_FAILED:
00110           fail++;
00111           delete cur;
00112           cur = NULL;
00113           Worker::current(NULL);
00114           break;
00115         case SS_SOLVED:
00116           {
00117             // Deletes all pending branchers
00118             (void) cur->choice();
00119             Space* s = cur;
00120             cur = NULL;
00121             Worker::current(NULL);
00122             return s;
00123           }
00124         case SS_BRANCH:
00125           {
00126             Space* c;
00127             if ((d == 0) || (d >= opt.c_d)) {
00128               c = cur->clone();
00129               d = 1;
00130             } else {
00131               c = NULL;
00132               d++;
00133             }
00134             const Choice* ch = path.push(*this,cur,c);
00135             Worker::push(c,ch);
00136             cur->commit(*ch,0);
00137             break;
00138           }
00139         default:
00140           GECODE_NEVER;
00141         }
00142       }
00143       do {
00144         if (!path.next(*this))
00145           return NULL;
00146         cur = path.recompute(d,opt.a_d,*this);
00147       } while (cur == NULL);
00148       Worker::current(cur);
00149     }
00150     GECODE_NEVER;
00151     return NULL;
00152   }
00153 
00154   forceinline Statistics
00155   DFS::statistics(void) const {
00156     Statistics s = *this;
00157     s.memory += path.size();
00158     return s;
00159   }
00160 
00161   forceinline 
00162   DFS::~DFS(void) {
00163     delete cur;
00164     path.reset();
00165   }
00166 
00167 }}}
00168 
00169 #endif
00170 
00171 // STATISTICS: search-sequential